JPS60120031A - Blow molding method and molding die thereof - Google Patents

Abstract

PURPOSE:To prevent generation of distortion and deterioration of the quality of a product, by a method wherein a thin fringe part for an opening is made to spread outward through inner pressure of parison by making an air bleeder pin pierced through a thin part of the parison retreat once and said pin is pierced through deeply again. CONSTITUTION:Parison 1 is molded into a predetermined shape by loading the parison 1 within a mold 2 and air is blown into the parison 1 through an air blowing nozzle. A thin part 1b is formed by making an expanding part 1a, which becomes an opening part of a final product, expand largely outward. After opening of the thin part 1b by piercing an air bleeder pin 16 through the thin part 1b while air is being blown in the parison and the thin finge part for opening has been made to spread outward through inner pressure of the parison by making said pin 16 retreat once, a part of the air in the inside of the parison is discharged through said air bleeder pin by piercing deeply said pin 16 again. As the thin part is formed and is broken through in two steps, excessive force which becomes a cause of distortion is not applied and there is no deterioration of the quality of a product.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a blow molding method mainly used for molding hollow containers and a mold thereof.

[Prior art]

Blow molding of hollow containers and the like is generally carried out as follows. First, thermoplastic resin is extruded into a cylindrical shape by an extrusion device of a molding machine (the extruded product is called a parison), and this parison is sandwiched between a pair of molds.

Then, compressed air is blown into the parison from the part that will eventually become the product opening, and the parison is pressed against the inner wall of the mold to form a predetermined shape.The resin is then left to cool for a certain period of time. Cure to obtain final product shape.

By the way, the cooling time mentioned above varies depending on the product shape and wall thickness, but it also accounts for 80 to 90% of the molding cycle, and increasing cooling efficiency is a major issue in making blow molding more efficient. ing. Therefore, cooling of the molded product is usually promoted by forming a cooling water passage in the mold and circulating the cooling water.

On the other hand, molded products that can be used for blow molding are not limited to so-called bottomed bottle-shaped products with one opening, but hollow containers with two or more openings (for example, vehicle fuel tanks, etc.). It is also applied to the molding of parisons, and in that case, a so-called air cooling method is used in which air is circulated within the parison to supplement the above-mentioned cooling of the cooling water.

To explain this using a vehicle fuel tank as an example based on the m1 diagram, the parison 1 extruded in advance by the extrusion device of the molding machine is sandwiched between a pair of molds 2a and 2b, while the opening 3 (the product The air blowing nozzle 4 is inserted into the air blowing nozzle (which sometimes serves as a mounting part for an outlet tube, etc.). Then, compressed air is blown into one round of the parison to expand it, and the parison 1 is pressed against the inner walls of the molds 2a and 2b. At this time, the air inside parison 1 has risen to nearly 200°C.

Next, after the parison 1 is sufficiently pressed against the inner walls of the molds 2a and 2b, the air bleed pin 6 is inserted into the core mold 5 embedded in one of the molds 2b while continuing to blow air. Here, the core mold 5 is installed at the part that will eventually become the product opening (fuel injection port), while the air bleed pin 6 moves back and forth by the action of the cylinder 7, and the inside is hollow. with the other end open to the atmosphere.

Therefore, at the same time as the air bleed pin 6 is inserted, a part of the parison 1 is torn by the air bleed pin 6, and the parison 1
A part of the high temperature air inside is discharged to the outside through the air bleed pin 6. In other words, by simultaneously blowing air from the air blowing nozzle 4 and removing a portion of the air using the air bleed pin 6, one yen of cool air is circulated in the parison 9, and the molds 2a, 2b. As a result, the cooling effect of the Valin x molded product) 1 will be further promoted.

It goes without saying that the cooling water flowing through the cooling water passage described above also provides a cooling effect, and the part torn by the air bleed bottle 6 is the part that will eventually become the product opening. Therefore, it does not pose any problem as a final product.

However, in the air cooling system as described above, the second
As shown in the figure, unreasonable force is applied to insert the air bleed bottle 6 into the uncured parison immediately after molding, which may cause distortion in the molded product.
When the pin is pulled out, resin adheres to the air bleed bottle 6, making the pin itself inoperable, and if the pin is forcibly pulled out, a portion of the resin breaks off and becomes entangled in the bottle.

[Purpose of the invention]

In view of the above points, the present invention provides a blow molding method and a mold for the same, which solve the above-mentioned conventional problems and enable smooth air cooling, which is the intended purpose. The purpose is to provide.

[Structure of the invention]

For this purpose, in the method of the present invention, the part into which the air bleed bottle is inserted is formed in advance to be thinner than other parts,
When the thin-walled portion is pierced by the air-bleeding bottle, the air-bleeding bottle is temporarily stopped, and at the same time, air is prevented from being discharged from the air-bleeding bottle. The portion is expanded outwardly by the internal pressure of the parison, and then the air bleed bottle is inserted deeply again to discharge part of the air inside the parison from the air bleed bottle.

According to the molding mold MVC of the present invention, an air-bleeding bottle is inserted into the part of the parison expanded in the mold that will become the opening in the final product, and the parison is expanded at the same time as air is blown. In a blow molding mold in which cooling of the parison is promoted by discharging 15 tl of internal air through the air bleed bottle, a bottle insertion hole is formed in a part of the mold to communicate between the inside and outside of the mold. and an air bleed bottle that is inserted into the pin insertion hole and breaks through a part of the parison by performing a stepwise forward movement, and the diameter of the pin insertion hole is set to be smaller than the diameter of the extraction pin. The outer wall thickness is set to be larger, and a counterbore is formed at the outer opening edge of the pin insertion hole.

〔Example〕

Hereinafter, more specific embodiments of the present invention will be described based on the drawings.

First, an embodiment of the method of the present invention will be explained using FIGS. 3 to 5. First, in FIG. 3, a parison 1 is sandwiched between a pair of molds as in the conventional method, and air is blown into the parison. Expand 1.

At this time, since the air bleed bottle 16 is waiting outside the mold without being inserted into the pin insertion hole 10, a part of the air bleed bottle 16 is bulged out near the opening end of the pin insertion hole 10 due to internal pressure. let

In other words, by forming a bulge 1a as a non-product part in a part of the parison 1 as a product part, the resin in the area corresponding to the bulge 1a is locally stretched, and the top of the bulge 1a is The thin portion 1b is formed by being significantly thinner than other portions.

Next, as shown in FIG. 4, the air bleed pin 16 is advanced and inserted into the pin insertion hole 10, and the tip of the air bleed pin 16 is inserted into the thin wall portion 1b. And air bleed pin 16
When the thin wall portion 1b is pierced by the air vent bottle 1,
6 is temporarily stopped, and the air bleed pin 1 is
Close the on-off valve (not shown) provided on the downstream side of 6, and open the parison 1.
This prevents the air inside from being discharged to the outside through the air bleed pin 16.

Even in this state, air is still blown into the parison 1 and pressurized, so the opening periphery of the thin wall portion 1b pierced by the air vent bottle 16 is pushed outward by the internal pressure of the parison 1. Expand to.

Then, after a certain period of time (3 to 5 seconds) has passed, air bleed pin 1
6 is moved forward by a certain amount again, and the opening/closing valve is opened. As shown in FIG. While maintaining the necessary shape-retaining pressure, the parison 1
A part of the air inside is discharged to the outside through the air bleed pin 16 and the on-off valve.

Needless to say, at this time, air is continuously blown into the parison 1.

In this way, according to the above embodiment, instead of breaking through a part of the parison 1 only by the pushing force of the air bleed pin 16, the movement of the air bleed pin 16 is temporarily stopped and the air is expanded by the internal pressure of the parison 1. Since the parison 1 is opened, no distortion occurs in the parison 1, and no resin gets entangled with the air vent bottle 16.

Next, an embodiment of the molding plate according to the present invention will be described using FIG. 6 in addition to FIGS. 3 to 5. The same parts as in Fig. 1 are given the same reference numerals.

In FIG. 6, 2a and 2b are a pair of molds, 15 is a core, 4 is an air blowing nozzle, 16 is an air bleed bottle,
This air bleed bottle 16 is moved forward and backward by the action of a multi-stage cylinder 17, and when moving forward, it performs a so-called two-motion, in which it moves forward intermittently over two stages.

Further, as shown in FIG. 3, if the diameter of the bottle insertion hole 10 formed in the core 15 is DI, the diameter of the air release pin 16 is 2, and the thickness of the resin in the bulging portion 1a is 't-t, The diameter of the bottle insertion hole 10 is set to be approximately equal to Ds+2t, while the inner open end of the pin insertion hole 10 is rounded (the radiused chamfer is indicated by reference numeral 15a), and the pin insertion hole 10 is rounded. In addition to preventing the parison 1 from being damaged when the parison 16 stops being pulled out, a counterbore 10& is formed at the outer open end so that the thin wall portion 1b can easily expand outward. (Detailed illustration is omitted in FIG. 6).

In the above configuration, the pair of molds 2a, 2
By sandwiching the parison 1 between the spacers b and blowing air from the air blowing nozzle 4, the parison 1 expands and
The parison 1 is pressed against the inner walls of the molds 2&, 2b and molded into a predetermined product shape (FIG. 6).

At this time, since the air bleed bottle 16 is not inserted into the pin insertion hole 1O, a part of the parison 1 swells up to near the outer opening end of the bottle insertion hole 1O due to its internal pressure, and expands including the thin wall portion 1bt. Exit part 1atl-form. At this point, 5 to 10 seconds have passed since air was blown (
Figure 3).

In the next step, due to the action of the multistage cylinder 17, the air bleed pin 6 moves forward by one step and is inserted into the bottle insertion hole 10, and its tip is thrust into the thin wall portion 1b (FIG. 4). At this time, the electromagnetic on-off valve 11 remains closed, and the air blowing from the air blowing nozzle 4 continues, so the opening peripheral edge of the thin wall portion 1b pierced by the air bleed bottle 16 is As shown in FIGS. 4 and 5, the parison 1 expands outward along the counterbore 10a due to the internal pressure of the parison 1.

Then, after 3 to 5 seconds have passed after the air bleed bottle 16 stops, the air bleed bottle 16 again performs the second forward movement, and at the same time the on-off valve 11 is opened, thereby maintaining the shape of the parison 1. A part of the air in the parison 1 is discharged to the outside through the air bleed bottle 16 and the on-off valve 11 while maintaining the necessary shape-retaining pressure. In other words, part of the air in the parison 1 is discharged by the air purge bottle 16 in parallel with the blowing of air from the air blowing nozzle 4.

According to the apparatus of this embodiment, the formation of the thin wall portion 1b makes it easy to break through the parison 1, and since no excessive force is applied, no distortion occurs in the parison, which is a molded product.

〔Effect of the invention〕

As explained above in detail, according to the method of the present invention, the parison is not pierced by only the pushing force of the air bleed bottle, but the air bleed bottle is operated in two stages to remove a part of the parison after being pierced. Since the parison is expanded by the internal pressure, there is no distortion due to the tight structure that prevents the application of excessive force to the parison, and the resin does not become entangled in the air release bottle, allowing molded products to be expanded. There is no deterioration in quality.

Further, according to the molding die of the present invention, a part of the parison is formed to be thin, so in addition to the above-mentioned effects, it becomes easier to break through the parison.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram for explaining the conventional blow molding method and molding die, Fig. 2 is an enlarged view of the main part of Fig. 1, and Figs. 3, 4, and 5 are illustrations of the method of the present invention. FIG. 6 is a sectional view showing an embodiment of the molding die of the present invention. DESCRIPTION OF SYMBOLS 1...Parison, la...Bulging part, Ill...Thin wall part, 2&, 2b...Mold, 4...Air blowing nozzle, lo...Pin insertion hole, 10a... Counterbore part, 15... core, 16... air release bottle. 2 people outside

Claims (2)

[Claims] (1) Insert an air bleed bottle into the part of the parison that has expanded in the mold due to air blowing, which will become the opening in the final product, and at the same time as air blowing, part of the air inside the parison is removed from the air bleed bottle. In a blow molding method in which cooling of the parison is promoted by discharging air, the part into which the air bleed bottle is inserted is formed in advance to be thinner than other parts, and the thin part is penetrated by the air bleed bottle. When the air bleed bottle is broken, the air bleed bottle is temporarily stopped and at the same time, air is prevented from being discharged from the air bleed bottle, while the opening periphery of the thin walled part pierced by the air bleed bottle is expanded outward by Parinon internal pressure. A blow molding method characterized in that a part of the air inside the parison is discharged from the air bleed bottle by deeply inserting the air bleed bottle again. (2) Insert an air bleed bottle into the part of the parison that has expanded in the mold due to air blowing, which will become an opening in the final product, and at the same time as air blowing, part of the air inside the parison is removed from the air bleed bottle. In a blow molding mold that accelerates the cooling of the parison by discharging it by It is fully equipped with an air bleed pin that is inserted into the insertion hole to break through a part of the parison, and the diameter of the bottle insertion hole is set larger than the diameter of the air bleed pin by the wall thickness of the parison. A blow molding die characterized in that a counterbore is formed at the opening edge on the pin insertion side of the hole.